The present invention relates to the field of compositions and methods used in connection with the application, maintenance and repair of asphalt paving. More particularly, the present invention relates to methods and materials used in sealing seams in asphalt paving.
One of the major problems that arises in applying the top course paving of a roadway is the sealing of the joint or “seam” between pavement sections or “lanes”. Since pavement sections are applied in widths determined by the width of the paver, they are typically applied in multiple passes of the paver, with each pass loosely referred to as a “lane”. This means that there is time interval between paving one lane and the next adjacent lane, during which time the asphalt of the preceding lane has cooled to ambient temperature. The temperature difference between the cooled pavement of the preceding lane and the fresh asphalt of the next adjacent lane makes for a weak bond between the two sections along the seam. This weakness often leads to cracking in the seam area, which allows water to penetrate into the seam and, with freezing and thawing, produces progressive deterioration and separation of the pavement sections.
Even when a strong bond is initially achieved in the seam between lanes, the expansion and contraction of the adjacent lanes under varying weather conditions will subject the seam to stresses and shear forces that will tend to degrade the joint over time and cause it to fail, due to the limited elasticity and tensile strength of asphalt paving materials. In effect, a paving seam has to function as an “expansion joint” between adjacent lanes, but the asphalt concrete typically applied in the seam area does not have the right mechanical properties to serve this function.
In an effort to address the problems associated with seam sealing, two approaches have been tried. The first approach is to reheat an area of the previously cooled lane adjacent to the seam to approximately the same temperature as the hot asphalt applied to the new lane, so that the reheated area will fuse with the fresh paving. An example of this method is taught by the patent application of Chandler (US2010/0021233). But the limited extent to which applied heat can penetrate downward and laterally into the asphalt of the preceding lane means that there will always be some juncture along which hot asphalt is interfacing with cooled asphalt, thereby producing a deficient bond.
The second approach to the seam sealing dilemma involves the use of a joint-sealing tape. Such tapes typically comprise a mixture of soft asphalt and rubber, and they are inserted into the seam after the two adjoining pavement sections have been laid down. An example of this method is described in the Hegemann U.S. Pat. No. 5,981,061. Problems associated with this method include gaps between the tape and the asphalt and failure of the tape to penetrate deeply enough into the seam. Furthermore, since this method involves applying adhesive between two pavement sections at ambient temperature, it misses the opportunity to use the elevated temperature of the fresh hot asphalt to improve the curing of the adhesive so as to form a stronger bond.
The present invention introduces a new method of sealing the seam between two adjacent sections of asphalt pavement. Instead of a tape applied after the adjoining sections have been paved, the present invention deploys an adhesive elastomeric gasket which completely envelopes the vertical faces of the adjacent lanes on three sides—i.e., above, below and along each face. Since the gasket extends partly underneath each section of paving, it is laid down before each lane is paved, thereby taking advantage of the heat of the fresh asphalt to effectively and rapidly cure the adhesive component of the gasket to insure a strong bond on both sides of the seam.